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No, he or she won't receive a notification, but you will disappear from the Friend list.
1.6. The absolute value of a positive number is that selfsame number.
Yes; if the "ly" ending didn't give it away, it's used to modify adjectives: considerably larger, considerably cheaper, etc.
Glasses vary very considerably in size.Glasses vary very considerably in size.Glasses vary very considerably in size.Glasses vary very considerably in size.
We are considerably older than our children.